Paper manufacture



Jan. 30, 1934. L. D. SMILEY 1,945,205

PAPER MANUFACTURE I v Filed Nov. 15. 1929- Patented Jan. 30, 1934 UNITED STATES PATENT OFFICE PAPER MANUFACTURE Lloyd D. Smiley, Dayton, Ohio, assignor, by mesne assignments, to Chemipulp Process, Inc., Watertown, N. Y., a corporation of New York Application November 15, 1929 Serial No. 407,394

20 Claims.

is to provide a more effective and eflicient process of digesting fibrous material utilizing a preheated cooking liquor.

Another. object is to provide a process which gives a better pulp product, and also adecreased time of treatment, and efiects recovery of gases and liquor resulting from the cooking process and of heat from such gases and liquor.

Still another object of the invention is to provide such a process in which accurate control of the temperature and concentration of the preheated and enriched cooking liquor is provided.

Still another object of the invention is to provide apparatus for carrying out the above method.

Other objects and advantages of the invention will be apparentv from the following description, the accompanying drawing and appended claims.

In the drawing, which discloses a preferred embodiment of the invention, the single figure is a diagrammatic elevational view of apparatus constructed for carrying out the method of this invention.

This invention has to do with the preparation of fibrous material for subsequent use in the making of paper and the like. Utilizing the apparatus shown, the fibrous material, such as wood chips, to be defibered, is introduced into a digester or digesters of suitable conventional construction wherein the cooking of the fibrous material is effected under heat and pressure. Two digesters numbered 10 and 11 respectively are shown in the particular arrangement of apparatus illustrated in the drawing, the cooking preferably being carried out in rotation. Each digester is provided with a filling opening 12 closed by a 0 suitable cover 13. Wood chips or other fibrous material are introduced into each digester from an overhead bin or chip conveyor (not shown) through the filling openings 12 upon the removal of the covers 13.

Cooking liquor is supplied to the digester by pipe 15 connected to thebottom of an accumulator 16, which is constructed as a closed tank lined with acid resisting material, wherein a supply of cooking liquor is adapted to be maintained under super-atmospheric pressure. The line 15 is connected to the lower portions of the digesters 10 and 11 by suitable branches 18 and 19 containing control valves 20 and 21 respectively. When a charge of fibrous material has been supplied to one of the digesters the cover 13 is replaced, and then sufiicient cooking liquor is supplied thereto from the accumulator 16 by opening the corresponding valve in the branch connecting the line 15 to the bottom of that digester. Steam under suitable pressure is then supplied to the digester through the steam line 22 to effect cooking there'- in. A steam pressure of '70 to 75 pounds per square inch will give good results with an acid sulphite liquor; but pressures below or in excess of this may be used.

The accumulator 16 is connected by a pipe line 25 with a raw cooking liquor storage tank 26. A pump 2'7 is shown within the line 25, for pumping the 1; quor from the storage tank 26 and introducing it into\the upper portion of the accumulator- 16. The raw cooking liquor of the acid sulphite process is generally formed in an acid absorption system wherein S02 gas is absorbed in lime water. An absorption tower 29 is ind cated diagrammatically herein. A plurality of these absorption towers are ordinarily used, the cooking liquor being supplied from this acid absorption systemto the storage tank 26 by piping indicated diagrammatically at. 30.

Each digester is provided with a gas relief pipe or line opening out of the upper end thereof- As shown, these lines pass through the covers 13, the

separate lines being indicated at 32 and 33 and having control valves 34 and 35 respectively. Each rel.ef line is connected to the bubbler pipe 36 which extends down into the accumulatortank 16 and is provided adjacent the bottom thereof with a perforated discharge end 37, so that the relief gas may be forced to bubble 'up through the cooking liquor within the accumulator, thereby enriching the cooking liquor and raising thetemperature of the whole body of the liquor in the accumulator. Each digest-er is also provided with a liquor relief line for the withdrawal of excess cooking liquor during the cooking operation, the

separate lines being indicated at 38 and 39 having control. valves 40 and 41 respectively, which are operated from the charging floor by means of suit.- able hand wheels 42 and 43 respectively. The gas relief line and the liquor relief line of each digester may thus be selectively connected to the accumulator by manipulation of the corresponding valves in the respective lines.

As shown, the gas relief line 32, as well as the liquor relief line 38 may be connected by piping 45 having a control valve 46 with suitable coolers indicated diagrammatically at 47, which are in turn connected by piping 48 having a control valve 49 with a cross pipe 50 having a control valve 51. The pipe 50 is in turn connected by piping 52 having a control valve 53 with. the bubbler pipe 36. The relief gas, or relief liquor, may thus be passed through coolers and thence introduced directly into the liquor within the accumulator tank 16. The gas relief line 32, and the liquor relief line 38, may also be directly connected with the bubbler pipe 36 by means of a-by-pass 54 hav-. ing a control valve 55 therein, the pipe 54 connecting directly with the pipe 52 whereby the coolers 47- are by-passed. The hot relief gases, or hot enrich and preheat this liquor. The digester 11,

including the gas relief line 33 and the liquor relief line 39, is provided'with a similar piping system indicated by the same numerals as used above.

For the purpose of passing the hot relief gases, or the hot relief liquor, in heat exchanging relation with the cooking liquor within the accumulator tank 16 without bringing the gases or the liquor into direct contact with the cooking liquor therein, a' closed heat exchange coil 58 is provided within the accumulator. One end 59 of this coil is connected by pipe 60 having a control valve 61 therein with the pipe 48 and with the pipe 50. a

a pipe 63, preferably containing therein a suitable cooler 64, with a bubbler pipe 65 which extends downwardly into the raw acid storage tank 26 and terminates in a perforate discharge end 66 at the bottom thereof. Thus relief gas from the digester'lo, for example, may be'passed through pipe 32, pipe 54, pipe 50, pipe 60 to the end 59 of coil 58, and thence from end 62 through pipe 63 to the storage tank 26. The sensible heat of the relief gas may thus be used to preheat the liquor within the accumulator 16 without further enriching this liquor, while at the same time the cooled relief gas may be absorbed in the raw cooking liquor in the acid storage tank 26.

The upper portion of the accumulator 16 above the normal liquid level therein is providedwith an ofltake pipe 68 having a suitable control valve 69 therein. This offtake pipe 68 may be connected to the pipe 63 below a suitable control valve '70 therein, or it may be connected directly tothe storage tank 26, whereby any excess gas not absorbed in the accumulator 16 may pass directly to the storage tank 26 and be introduced into the raw cooking liquor contained therein. Any as not absorbed in the storage tank 26 may pass off through the vent pipe '72 to the absorption tower 29, whereby substantially all oi. the sulphur dioxide or active cooking gas is recovered and returned to the system. The liquor relie! lines 38 and 39 may also be provided-with additional control valves '74 and '75 respectively adjacent the point -of connection ,of the lines 38 and 39 with the pipes 45 and 54.

Also connected to the upper portion of each digester, shown as opening through the covers 13, is a vacuum line '78 connected to, a suitable vacuum pump '79, whereby the digesters may be enriched liquor may be fed from the accumulator to the digesters by the hydrostatic head. In operation, assuming that one o! the digesters 10 has been supplied with fibrous material, the cover 13 is replaced and then the valve 20 in the line 18 is openedto permit cooking liquor to flow from the accumulator 16 past valves and 81 within the pipe 15 to the pipe 18 and thence into the digester. At this time, the pump '79 is placed in operation to evacuate the space within the digester 10. This produces a sub-atmospheric pressure in thedigester-which facilitates impregnation or the cooking liquor with the fibrous-material therein. By. reason or the fact that the charge'o! cooking liquor from the accumulator 16 is in a preheated condition when it is first brought into contact with the fibrous material. superior results are obtained. Thus a more .even

penetration of the liquor within the fibrous material and a uniform heating up and initial cook-V pump 85 which is connected to the line 15 by pipes 86 and 87 containing control valves 88 and 89 respectively the valve 81 being then closed. This pump 85 may then be operated to force the liquor into the digester to completely fill the same and establish a high hydraulic pressure within the digesterto further facilitate impregnation of the chips by the liquor.- For example, the pressure may be raised as high as 100pounds per square inch or higher in order to positively force the liquor into the evacuated chips. Before steam is Theintroduced from the line 22, the excess liquor is ing. This may be accomplished by a second pump 90 connected to the pipe 15 by pipes 91 and 92 containing therein suitable control valves 93 and 94 respectively, the pump 90 serving to draw liquor from the tank and force it back into the digester, the valves 81. 88 and 89 being closed at this time. Steam is then introduced through the line 22 to increase the temperature or the cooking liquor and correspondingly increase the cooking effect, the cooking being carried out under heat and pressure as described above. A suitable pressure differential is maintained between the digester and the accumulaton so that relief gas and. relief liquor may be forced during the cooking operation from the digester to the accumulator. For example, with a cooking pressure of about 60 to 86 pounds per square inch, 9. pressure of about-20- to 50 pounds per square inch maybe maintained within the accu'mulaton- Con trol of the pressure within the accumulator is had by variation of the positioning of the valve 69 in the ofitake pipe 68.

- As the cooking progresses, and the digesteris brought up to higher temperatures and pressures, hot gas is liberated from the cooking liquor tending to build up a false pressure. The valve 34 in the relief line 32 is then opened to permit a controlledescape of the liberated gas to thereby maintain the temperature and pressure in the digester at the proper values. This gas may be introduced directly into the cooking liquor which has been supplied to the accumulator 16 from the acid storagetank 26, or it may. e merely passed in heat exchanging relation with-the liquor with-' in this tank. Thus by opening valves 34, 46, 49, 51 and 53, the other valves being closed, the relief gas may be passed through coolers 47 and thence through bubbler pipe 36 into the liquor within the accumulator to thereby enrich this liquor without a substantial heating eiiect. On the other hand, by opening valves 34, 55 and 53, the

other valves being closed, the hot gasmay be passed directly without substantial cooling into the'liquor within the accumulator to both preheat and enrich the liquor. Any gas not absorbed within the accumulator 16 passes oil by the pipe 68- and pipe 63 into the raw cooking liquor within 1 the storage tank 26, or eventually by the veutpipe '72 into the acid absorption system 29, and iamcovered. Or byopening valves 34, 55, 51 and 61,

the other valves being closed, the hot relief gas' Y may be passed through the coil 58 without being brought into absorbing contact with the liquor within theaccumulator 16, to thereby heat this liquor to a desired high temperature. Relic! liqthrough the cooking liquor within said accumuor liberated by the liquor relief line 38 may similarly pass directly into the accumulator without cooling, or through the cooler and thence'into the accumulator, or through the heat exchange coil 58 and thence into the storage tank 26. In this manner, the temperature and the concentration of the liquor within the accumulator 16 may be independently controlled, so that more uniform cooking of the fibrous material with this liquor for different cooks is insured. The temperature of the liquor within the accumulator may be brought up to as high as 180 F. or higher, while at the same time complete absorption of-the liberated gas within the system is insured.

The accumulator 16 is constructed of a size to hold at least a charge of cooking liquor for a sin gle digester. During the cooking in one digester 10, the other digester 11 is charged with fibrous material'so that at the termination of the cook in the first digester 10, the valve 34 in the relief line 32 of that digester may be closed andthevalve 21 in the liquor line l--l9 of the other digester 11 may be opened so as to feed the preheated and enriched liquor from the accumulator 16 into contact with the chips within the closed digester 11. The evacuation and the placing of the liquor under high pressure may be carried out in the digester 11 as described above. The valve 21 is then closed and steam introduced through the line 22. Fresh liquor is then supplied to the accumulator 16 through the line 25 by pump 27. When the digester 11 is brought up to pressure, the valve in the gas relief line 33 is opened so that the relief gases from that digester may pass into the accumulator 16 as described above. The first digester 10 is then refilled with fibrous material and the cycle repeated.

This method and apparatus effect material economy in operation, in that the sensible heat in the relief gas is conserved. As a result the liquor supplied to the digester is in a preheated condition and the resulting cook takes place more efiectively and rapidly to produce a better prod, not. Also less steam is required for heating the liquor in the digester to effect proper cooking, and there is less condensation of steam within the cooking liquor in the digester. Inasmuch as the liquor is already highly heated, objectionable water hammer when steam is first introduced into the digester is avoided. Also longer life of the digester is insured, inasmuch as the magnitude of rapid temperature changes, which deleteriously affect the lining of the digester, is reduced. Accurate control of the concentration and the temperature of the preheated and enriched cooking liquor to be added to the fibrous material is also readily secured, so that uniformity of results by successive cooks is obtained.

While the method herein described, and the form of apparatus for carrying this method into effect, constitute preferred embodiments of the invention, it is to be understood that the inven-' 'tion is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. Apparatus of the character described, com prising a digester for cooking fibrous material with cooking liquor under pressure, a pressure accumulator for confining a supply of cooking liquor under super-atmospheric pressure, a gas relief line connecting said digester with said accumulator to permit the hot relief gas to pass lator to thereby conserve heat and gas, said accumulator being positioned at a higher elevation than said digester, and a gravity feed pipe for introducing the heated and enriched cooking liquor from said accumulator into said digester.

2. Apparatus of the character described, com

prising a digester for. cooking fibrous material with cooking liquor under pressure, a pressure accumulator for confining a supply of cooking liquor under super-atmospheric pressure, a gas relief line connecting said digester with said accumulator to permit the hot relief gas to passin heat exchanging relation with the cooking liquor within said accumulator to thereby heat the liquor, means for introducing the heated cooking liquor from said accumulator into said digester, and means for producing a sub-atmospheric pressure within said digester.

3. Apparatus of the character described, com

prising a digester for cooking fibrous material with cooking liquor under pressure, an accumulator for holding a supply of cooking liquor, a gas relief line for said digester, a bubbler pipe for the accumulator, a closed heat exchange pipe for the accumulator, and means for selectively connecting said gas relief pipe with said bubbler pipe and with said heat exchange pipe.

4. Apparatus of the character described, comprising a digester for cooking fibrous material with cooking liquor under pressure, an accumulator for holding supply of cooking liquor, a gas relief pipe for said digester, a heat exchange pipe for said accumulator, one end of said heat exchange pipe being connected to said gas relief pipe, a raw cooking liquor storage tank, means for supplying raw cooking liquor from said storf age tank to said accumulator, and means for connecting the other end of said heat exchange pipe with said storage tank to introduce the cooled,

relief gas into the raw cooking liquor within said storage tank.

5. Apparatus of the character described, com-v prising a digester for cooking fibrous material with. cooking liquor under pressure, an accumulator for holding a supply .of cooking liquor, a gas relief pipe for said digester, a heat exchange pipe for said accumulator, one end of said heat exchange pipe being connected to said gas relief pipe, a raw cooking liquor storage tank, means for supplying raw cooking liquor from said storagetank to said accumulator, means for connecting the other end of said heat exchange pipe with said raw cooking liquor storage tank, a gas absorption system for forming raw cooking liquor, a vent for said storage tank, and means for connecting said vent with said gas absorption system.

6. Apparatus of the character described, comprising a digester for cooking fibrous material with cooking liquor under pressure, an accumulator for holding a supply of cooking liquor, a gas relief pipe for said digester, a cooler, a by-pass around said cooler, a pipe within said accumulator, and means for connecting said gas relief pipe with said pipe within the accumulator through said cooler or directly through said by-pass around the cooler.

'7. Apparatus of the character described, comprising a digester for cooking fibrous material with cooking liquor under pressure, an accumulator for holding a supply of cooking liquor, a gas relief line for said digester, a cooler, a by-pass around said cooler, a bubbler pipe within said accumulator, a closed heat exchange pipe for said accumulator, and means for selectively connecting said gas relief pipe with said bubbler pipe or said closed heat exchange pipe through said cooler. I

8. Apparatus of the character described, comprising a digester for cooking fibrous material with cooking liquor under pressure, a pressure ac,- cumulator for confining a supply of cooking liquor under super-atmospheric pressure, a gas relief pipe for said digester, a liquor relief pipe for said digester, a heat exchanger in the accumulator, and means for selectively connecting said gas relief pipe and said liquor relief pipe with said accumulator or said heat exchanger to thereby con serve gas and liquor and the sensible heat thereof.

9. Apparatus of the character described, comprising a digester for cooking fibrous material cooler or directly through said by-pass around the with cooking liquor under pressuraan accumula tor for holding a supply of cooking liquor, heating means for the accumulator to preheat cooking liquor therein to a high temperature, and means for introducing relief'fiuids from said digester into 'said heating means or into contact with the supply of cooking liquor-within said accumulator.

10. Apparatus of the character described, comprising a digester for cooking fibrous material with'cooking liquor under pressure, an accumulator for holding a supply of cooking liquor, heating means for the accumulator to preheat cooking liquor therein to a high temperature, means for introducing preheated cooking liquor from said accumulator into contact with fibrous material within said digester, and means independent of said heating means for producing sub-atmospheric pressure within said digester.

11. Apparatus for 'the character described, comprising a digester for cooking fibrous material with cooking liquor under pressure, an accumulator for holding a supply of cooking liquor, heating means for the accumulator to preheat cooking liquor therein to a high temperature, means for. introducing preheated cooking liquor from said accumulator into contact'with fibrous material within said digester, means for producing sub-atmospheric pressure within said digester,

and a hydraulic pump for increasing the pressure within said digester to facilitate impregnation of fibrous material therein with the cooking liquor. Q

12. The method of treating fibrous material which comprises introducing the fibrous material into a normally closed chamber, preheating a supply of cooking liquor, bringing the preheated cooking liquor at an elevated temperature into contact with fibrous material within the closed chamber, evacuating the chamber to facilitate impregnation of the fibrous material by the cooking liquor, and then subjecting the fibrous material to additional cooking with the cooking liquor under heat and pressure.

13. The method of treating fibrous material which comprises introducing the fibrous material into a normally closed chamber, preheating a supply of cooking liquor, bringing the preheated cooking liquor at an elevated temperature into contact with fibrous material within the closed chamber, evacuating the chamber to facilitate impregnation of the fibrous material by the cooking liquor, producing a hydraulic pressure of cooking liqour within the closed chamber to further facilitate impregnation, and subjecting the fibrous material to additionalcooking with the preheated cooking liquor under heat and pressure.

14. The method of treating fibrous material which comprises introducing fibrous material into a normally closed chamber, introducing pre- A heated cooking liquor into contact with the fibrous material within the. normally closed chamber, evacuating the chamber during the introduction of the cooking liquor into the chamber-,and then cooking the fibrous material with chamber, passing some of the hot relief fluid in heat exchanging relation with additional cboking liquor to preheat the cooking liquor and lalso passing some of the hot relief fluid directly into the last mentioned cooking liquor, and using the preheated cooking liquor to cook additional fibrous material.

16. The method of treating cooking liquors for the sulphite process of making pulp which comprises relieving a sulphite digester during its operation, discharging some of therelief mate rials under pressure into a confined volume of liquor, discharging some of the relief materials through said confined volume of liquor-in indirect heat exchange with said liquor relief material to said volume of liquor. Y

17. Apparatus for the sulphite process of producing pulp which comprises a digester, relief means for the digester, an accumulator adapted to store raw cooking liquor under pressure, heat transfer means associated with the accumulator, and valved means for connecting the relief means for discharging into the accumulator and through the heat transfer means.

18. Apparatus for the sulphite process of producing pulp which comprises a digester, relief means for the digester an accumulator adapted to store under pressure a full charge of cooking liquor for the digester, heat transfer means for the accumulator, valved means for connecting the relief means for discharging into the accumu- .cating means between the digester and'the accumulator for admitting theaccumulator charge into the digester.

19. Apparatus for charging pulp digesters with liquor which comprises an accumulator adapted to hold cooking liquor under pressure, means for discharging into the accumulator suitable gases for absorption by the liquor, means to heat the cooking liquor in the accumulator, and a discharge conduit for conducting the liquor into the digester.

20. In the sulphite process of cooking cellulosic material for the production of pulp, passing hot relief fluids from a digester during cooking directly into a closed accumulator arranged entirely above the digester, and thus preheating and strengthening a supply of cooking liquor in the accumulator under super-atmospheric" pressure, placing cellulosic material in a digester, and causing the preheated and supply of cooking liquor to flow-from said ac:

cumulator to the digester by gravity and under said super-atmospheric pressure.

LLOYD D. SMILEY.

preconditioned sen 

